EP0191657A1 - Method for radioelectrically synchronizing stations of an MLS landing aid system by a DME station, and devices for carrying out such a method - Google Patents

Method for radioelectrically synchronizing stations of an MLS landing aid system by a DME station, and devices for carrying out such a method Download PDF

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Publication number
EP0191657A1
EP0191657A1 EP86400022A EP86400022A EP0191657A1 EP 0191657 A1 EP0191657 A1 EP 0191657A1 EP 86400022 A EP86400022 A EP 86400022A EP 86400022 A EP86400022 A EP 86400022A EP 0191657 A1 EP0191657 A1 EP 0191657A1
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EP
European Patent Office
Prior art keywords
station
dme
mls
receiver
pulses
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EP86400022A
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German (de)
French (fr)
Inventor
Alain Grousseau
Joseph Hetyei
Bruno Letoquart
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Thales SA
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Thomson CSF SA
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S1/00—Beacons or beacon systems transmitting signals having a characteristic or characteristics capable of being detected by non-directional receivers and defining directions, positions, or position lines fixed relatively to the beacon transmitters; Receivers co-operating therewith
    • G01S1/02—Beacons or beacon systems transmitting signals having a characteristic or characteristics capable of being detected by non-directional receivers and defining directions, positions, or position lines fixed relatively to the beacon transmitters; Receivers co-operating therewith using radio waves
    • G01S1/08—Systems for determining direction or position line
    • G01S1/44—Rotating or oscillating beam beacons defining directions in the plane of rotation or oscillation
    • G01S1/54—Narrow-beam systems producing at a receiver a pulse-type envelope signal of the carrier wave of the beam, the timing of which is dependent upon the angle between the direction of the receiver from the beacon and a reference direction from the beacon; Overlapping broad beam systems defining a narrow zone and producing at a receiver a pulse-type envelope signal of the carrier wave of the beam, the timing of which is dependent upon the angle between the direction of the receiver from the beacon and a reference direction from the beacon
    • G01S1/56—Timing the pulse-type envelope signals derived by reception of the beam

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  • the present invention relates to a radio frequency synchronization method for stations of an MLS type landing aid system, such as azimuth and site stations, by a DME type station.
  • the invention also relates to devices for implementing this method.
  • an MLS type landing aid system (initials of the English expression Microwave Landing System) makes it possible to provide an aircraft with various information - called “functions" - on its position, in particular the azimuth angle and angle of elevation in a coordinate system linked to the airstrip, as well as, possibly, other auxiliary functions such as the rear azimuth for example, and a certain number of data, the so-called “basic” and the others called “auxiliary”.
  • This different information is transmitted by the MLS system alternately from the ground, in time multiplexing on the same frequency, close to 5 GHz, according to characteristics standardized by the International Civil Aviation Organization (ICAO), appendix 10 , paragraph 3-11.
  • IAO International Civil Aviation Organization
  • Figure 1 shows a frequent arrangement of azimuth and site MLS stations around an airstrip.
  • the azimuth station (A Z ) is close to the end of the runway, marked P and of axis ZZ. This station transmits in the direction of runway P, thus enabling the aircraft (Ay) to have the azimuth angular information during the entire landing, and this even during the taxiing phase on the runway.
  • the site station (S) transmits in the same direction but it is on the other hand close to the entry threshold of runway P, allowing the aircraft Ay to be guided on a trajectory at constant site angle during the landing, and to be brought by this trajectory at the start of the runway.
  • the azimuth and site stations are generally placed in relation to each other at a distance of several kilometers.
  • An MLS system may include other stations (rear azimuth, data), not shown in Figure 1.
  • a MLS type landing aid system in principle comprises distance measurement equipment called DME (for Distance Measuring Equipment in English), located either in one of the azimuth or site MLS stations, or at near one of them.
  • DME distance Measuring Equipment in English
  • FIG. 1 shows a DME station marked D, placed near the azimuth station A Z. " Station D permanently supplies aircraft A V with the distance separating it from station D (that is to say from the end of runway P in the case of FIG. 1), including in its rolling phase on the track.
  • the operation of a DME system is as follows: the aircraft (A V ) carries a DME interrogator which interrogates the ground station (D), called a transponder.
  • the interrogation message consists of a pair of pulses whose spacing and carrier frequency are defined by ICAO standards and known to the transponder.
  • the transponder receives and recognizes these pulses, it sends a response to the aircraft.
  • the response is also a pair of pulses, spacing and carrier frequency known to the interrogator, transmitted with a constant and known delay, the whole being also defined by the ICAO standards.
  • the aircraft interrogator receives and recognizes these response pulses, it deduces the distance which separates it from the DME station from the duration of the round trip of the pulses.
  • the DME station operates, according to ICAO standards, on a frequency (close to 1 GHz) completely separate from that of the MLS stations (close to 5 GHz).
  • ICAO Integrated Multimedia Subsystem
  • the time-sharing operation on the same frequency of the various MLS stations requires the existence of a time synchronization link between these MLS stations, in order to ensure the non-recovery of emissions.
  • the azimuth station plays the role of master station, but this is not compulsory.
  • the master station must therefore send synchronization signals to the other MLS stations, called slave stations, to enable them to transmit at the desired time.
  • This synchronization of MLS stations with one another can be achieved by physical link, electrical cable or optical fiber for example.
  • it then has the disadvantage of being expensive because of the civil engineering work which it entails, in particular the construction of trenches over distances of up to several kilometers.
  • the invention relates to a method avoiding this drawback by the fact that it ensures radio synchronization. More specifically, it ensures the synchronization of at least one MLS station (slave station) by the DME station associated with another station of the MLS system, playing the role of master station, according to the method such as defined by claim 1.
  • FIG. 1 therefore represents the general organization of the MLS-DME system, synchronized according to the invention.
  • the system according to the invention furthermore comprises a DME type DME receiving station, located in the slave station (site) or close to it.
  • the DME station D in order to synchronize one or more slave MLS stations with a master MLS station, the DME station D also transmits synchronization information, called S YD , intended for a DME type receiver, denoted D S and located in or near each of the slave MLS stations; in the example of FIG. 1, there is only one slave station, the site station S, and this transmission is represented by an arrow d S.
  • This synchronization transmission is made on command, denoted S YA , from the master MLS station (the azimuth station).
  • the DME station D being placed in the example of FIG. 1 near the azimuth station, but not inside the latter, a connection must be made between these two stations, preferably by cable.
  • the DME D S receiver being placed (still in the example in FIG. 1) near the site station, that is to say at a distance of the order of a few meters, the necessary connection between the two stations is also preferably by cable.
  • the synchronization information received by the receiver DME D S and transmitted to the station MLS S is noted S YS '
  • the slave MLS station also transmits the operating or non-operating state E in which it is located to the master station (azimuth station), this transmission also taking place by via the DME station as shown by the dotted arrows in FIG. 1: by cable, the site station S transmits its status E to the DME station D S , which transmits this information to the DME D station by radio (arrow d E ); on receipt of this status information, the DME station D transmits it to the azimuth station A Z also by cable.
  • the site station S transmits its status E to the DME station D S , which transmits this information to the DME D station by radio (arrow d E ); on receipt of this status information, the DME station D transmits it to the azimuth station A Z also by cable.
  • the system according to the invention therefore uses a DME (D) transponder of the conventional type, to which a particular coder adapted to the transmission of the synchronization information S YD is added and, if necessary, a particular decoder for receiving state information E, and at least one additional DME type station, located near the slave MLS station (s), mainly comprising a receiver and a decoder for synchronization information, to which are preferably added a local clock and a system for controlling this clock on the clock of the master station and, where appropriate, a set of transmitting state information E of the slave station.
  • DME DME
  • the MLS system is described below in more detail.
  • FIG. 2 is a diagram of the conventional general organization of an angle station of an MLS system, azimuth or site for example.
  • This station essentially comprises a transmitter 1, two antennas: a sectoral antenna 3 and an antenna with electronic scanning 4, and control circuits (2, 5).
  • the transmitter 1 supplies a signal, via a switch 2, either to the sectoral antenna 3 for the transmission of the preamble and the data, basic or auxiliary, or to the scanning antenna 4.
  • the latter (4) is conventionally broken down into a power divider (or distributor), dividing the power received from switch 2 into N in order to supply N digital phase shifters, which supply N radiating elements; the values of the phase shifts introduced by the phase shifters are controlled by a scanning logic circuit, in order to carry out an electronic scanning from static radiating elements.
  • the entire station is therefore controlled by the microprocessor 5 and its memory, connected to the transmitter 1, to the switch 2 and to the scanning antenna 4, by means of its scanning logic circuit, the microprocessor 5 providing the scanning logic circuit with the start time of the scanning for the angle functions.
  • the microprocessor 5 supplies (arrow 50) the synchronization signal S YA to the DME station D.
  • the microprocessor 5 supplies; if necessary, information E on the state of the station at the station DME D S.
  • Each of the MLS stations therefore transmits in turn according to a predefined and periodic sequencing, standardized by the ICAO, called cycle and whose duration is 615 ms.
  • Generating an MLS cycle in real time means generating the status word in real time in the microprocessor, which then performs the various commands. To this end, the succession of status words corresponding to the desired cycle is stored in a table in the memory of the microprocessor 5. At the rhythm of a suitable clock, the microprocessor 5 will seek the successive state words and supply them to an interface (not shown), of the PIA type (for "Parallel Interface Adapter") for example, which controls the various blocks of MLS station.
  • PIA type for "Parallel Interface Adapter"
  • FIG. 3 represents the general diagram of a DME D type transponder.
  • Such a transponder comprises an antenna A D , capable of transmitting and receiving DME transmissions on the standardized frequencies, close to 1 MHz; it is connected to a diplexer D I , the function of which, as is known, is to provide the connection of the antenna A D alternately with a receiver R X and a transmitter T X of the transponder D.
  • the receiver R x has the function of amplifying and detecting the pulses in the signals received by the antenna A D , as well as of decoding these signals, that is to say of taking into consideration only those which have as carrier frequency the DME frequency assigned to the transponder in question and that the pairs of pulses whose spacing corresponds to the normalized DME spacing.
  • the transponder When a received signal has been recognized by the receiver R X as DME interrogation pulses, the transponder must develop a response, also consisting of two pulses transmitted at a determined frequency and spaced apart by a determined time interval. These response pulses are developed in a encoder C, on command of receiver R X. They are transmitted to the transmitter T X for transmission by the antenna AD via the diplexer D r
  • the transmitter T X and the receiver R X are controlled by a local oscillator Op, which supplies the transmitter T X with the transmission frequency of the transponder (around 1 GHz) and the receiver R X with the frequency necessary for changing frequency (it is recalled that if the transponder transmission frequency is equal to F o , the aircraft interrogator transmission frequency is equal to F o + 63 MH z ).
  • the transponder D also has the function of transmitting synchronization information (S YD ) to the DME receiver D S (FIG. 1). To this end, it receives from the azimuth station A Z a synchronization signal S YA which, applied to the encoder C, triggers by the latter the emission of the synchronization information in the form of pulses, the number and l spacing are chosen to be distinct from conventional DME pulses.
  • the synchronization pulses produced by the encoder C are then transmitted to the transmitter T X and then to the antenna A D like the conventional pulses.
  • each DME channel is associated with a DME channel, defined by its frequency (between 962 and 1150 MHz in steps of 1 MHz) and its code, that is to say the spacing between two pulses of a pair ( four separate codes between 12 and 42 us, the width of the DME pulse at mid-height being 3.5 ⁇ s).
  • Synchronization information is sent on the response frequency assigned to the transponder in question, in the form of at least two pulses, with a code different from those used by the DME.
  • the number of three constitutes a good optimum between safety. and simplicity.
  • FIG. 4a is the diagram of an embodiment of the coding device C according to the invention, ensuring the generation of both conventional response pulses from the DME transponder and synchronization pulses.
  • the device C therefore comprises an encoder C D developing the conventional response of a DME transponder, receiving an emission command from the receiver R X and transmitting the pulses which it has produced to the transmitter T X , and more precisely to the modulator that it comprises by means of a logic circuit C L.
  • the device C comprises a second encoder C SY which has the function, on reception of the synchronization signal S YA coming from the azimuth station A Z , of generating the synchronization pulses intended for the transmitter T X , via the circuit logic C L which makes it possible to avoid any conflict of access to the transmitter T X between the two coders CD and C SY .
  • the coder C SY can advantageously be produced like the coder C D , which, conventionally, is produced from a shift register or a counter.
  • FIG. 4b represents an embodiment of the logic circuit C L.
  • the circuit C L comprises: two logic gates, one of the AND type marked 11 and the other of the non-exclusive OR type marked 12; a circuit 13 such as a monostable, making it possible to generate a signal ensuring the priority of the synchronization information over the information coming from the encoder C D ; an inverter 15 placed at the output of circuit 13, and a circuit 14, such as a monostable, connected between the encoders C SY and the OR gate 12.
  • this circuit is as follows, illustrated by the diagrams in Figure 4c: on command of the pulse synchronization S YA , represented on the first line of FIG. 4c, the synchronization coder C SY generates a series of pulses representing the synchronization information; three of these pulses are shown by way of example in the second line of FIG. 4c. These pulses are applied on the one hand to the circuit 13 and on the other hand to an input of the OR gate 12, via the monostable 14.
  • the devices 13 and 15 In the presence of synchronization information to be transmitted, the devices 13 and 15 generate signals (shown in Figure 4c at the output of circuit 13) such that they inhibit, through the AND gate 11, the passage of signals from the encoder C D ; the synchronization signals then pass through the OR gate 12, via the monostable 14. In the absence of synchronization information, the information coming from the encoder C D reaches the transmitter T X by successively AND gates 11 and OR 12.
  • the function of circuit 14 is to give a delay to the synchronization pulses coming from the encoder C SY , as shown on the last line of FIG. 4c, in order to avoid any coincidence with a DME pulse in origin of coder C D ; the value of the delay thus conferred, of the order of 10 ⁇ s, constitutes the synchronization protection time Tp mentioned above.
  • FIG. 5 represents the diagram of an embodiment of the DME D S receiver used for the synchronization of a slave MLS station.
  • This receiver D S comprises the conventional elements of a DME receiver, namely: an antenna marked A S and a receiver, detector and decoder R XS , controlled by a local oscillator Op S. It further comprises a device 30, called an MLS sequencer; the function of this sequencer 30 is to run the MLS cycle from the reception of the synchronization information; it is produced for example using a microprocessor and provides synchronization information S YS to the slave MLS station, the site station S in this example, synchronization information which will trigger the transmission of the MLS function by the slave station.
  • the antenna A S is a directive antenna, oriented towards the DME D station and capable of receiving its emissions.
  • the function of the receiver R XS is to amplify, to detect the signals received by the antenna A S and to decode and recognize the pulses received in order to supply a synchronization pulse S m each time the series of synchronization pulses expected is received from the master station, via the DME station.
  • the pulse S m is used directly for triggering the MLS 30 sequencer.
  • the receiver D S further comprises a clock H and a set of electronic circuits 20 to 29 intended to generate, from the period of the clock H, a signal of synchronization at the start of each MLS cycle, as well as to control this clock H on the synchronization signal received by the receiver R XS .
  • the frequency of the local clock H is divided by a number N using a device 20, produced for example by a counter, in order to provide a synchronization pulse in periods of 615 ms which is, as we recall, the normalized duration of the MLS cycle.
  • the time reference of the station D S is controlled both for short-term drifts and for long-term drifts.
  • the correction of short-term drifts is carried out by resetting (reset input) the counter 20 by the synchronization signal S M.
  • the correction of the long-term drifts of the clock H is carried out by modifying the division rank of the counter 20 by a value equal to ⁇ An using the circuits 21 to 29, which receive the signals S M and S E .
  • the two monostables 27 and 28 are at rest, their output being at level 1.
  • the signal SE passes through the AND gate 25 and occurs at the input S of the flip-flop 24.
  • the output Q of this flip-flop is connected to a selection input (up or down) of an up-down counter 22; in the present case, it positions the device 22 so that it counts towards the increasing numbers when it receives a pulse coming from a monostable 23, which receives the signal S M.
  • the latter signal is received by the monostable 23, it therefore causes the initial value n of the counter 22 to increase by one unit.
  • the presence of the signal SE on the input of the monostable 28 changes the output state.
  • the function of the delay circuit 29 is as follows: the fact that the signal S m resets the counter 21 to zero each time it is present, an output pulse being produced by this counter each time its content is equal to zero, there would be a signal SE whenever a signal S m is present; the delay circuit 29, which introduces a delay of the order of a few hundred nanoseconds, considered to be negligible compared to the durations Tp and T C , makes it possible to ensure the advance of the signal S M over the signal SE.
  • another counter, marked 31 is used to count the autonomy time of the station D S : it stops the transmission from the slave station when the latter no longer receives the synchronization pulse S M during a predefined time interval, and it is reset to zero each time an S M pulse is received.
  • the counter 31 can also provide a pre-alarm signal on an intermediate value of its content.
  • the DME station D S In the alternative embodiment described in FIG. 1 in which the slave station, site for example, transmits information on its state to the DME D S station , which retransmits it to the DME D station by radio, intended for the master station A Z , the DME station D S must then also include, analogously to what is shown in FIG. 3, a coding circuit coding the status information of the slave station according to a specific code, that is to say ie in the form of a series of pulses whose spacing is distinct from the previous ones, and a transmitter of this information coded, at the interrogation frequency assigned to the DME station considered, and transmitting it to the antenna A S of the station D S via a diplexer.
  • the DME D station must also include a decoder adapted to recognize the status information of the slave station.
  • information can be transmitted between the MLS stations and outside via the DME station, other than synchronization or status information, such as the remote control or the remote control of the MLS stations from the airport control tower, provided that DME transmitters and receivers are added where necessary.

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  • Physics & Mathematics (AREA)
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  • Radar, Positioning & Navigation (AREA)
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Abstract

According to the method, one of the (for example azimuth) MLS stations is selected as master station. It transmits the synchronisation (SYA) to the DME station (D) which, installed near-by, sends this synchronisation signal (SYD) by radio means to a DME receiver (DS) installed on the (for example elevation) MLS slave station side. The synchronisation signal transmitted is coded in the form of a plurality of successive pulses, the spacing of which differs from that for the pulses of the conventional DME transmissions. <IMAGE>

Description

La présente invention concerne un procédé de synchronisation radioélectrique de stations d'un système d'aide à l'atterrissage du type MLS, telles que les stations azimut et site, par une station de type DME. L'invention a également pour objet des dispositifs de mise en oeuvre de ce procédé. The present invention relates to a radio frequency synchronization method for stations of an MLS type landing aid system, such as azimuth and site stations, by a DME type station. The invention also relates to devices for implementing this method.

On rappelle qu'un système d'aide à l'atterrissage de type MLS (initiales de l'expression anglo-saxonne Microwave Landing System) permet de fournir à un aéronef différentes informations - appelées "fonctions" - sur sa position, notamment l'angle d'azimut et l'angle de site dans un repère lié à la piste d'atterrissage, ainsi que, éventuellement, d'autres fonctions annexes telles que l'azimut arrière par exemple, et un certain nombre de données, les unes dites "de base" et les autres dites "auxiliaires". Ces différentes informations sont émises par le système MLS en alternance, à partir du sol, en multiplexage temporel sur une même fréquence, voisine de 5 GHz, selon des caractéristiques normalisées par l'Organisation de l'Aviation Civile Internationale (OACI), annexe 10, paragraphe 3-11.It is recalled that an MLS type landing aid system (initials of the English expression Microwave Landing System) makes it possible to provide an aircraft with various information - called "functions" - on its position, in particular the azimuth angle and angle of elevation in a coordinate system linked to the airstrip, as well as, possibly, other auxiliary functions such as the rear azimuth for example, and a certain number of data, the so-called "basic" and the others called "auxiliary". This different information is transmitted by the MLS system alternately from the ground, in time multiplexing on the same frequency, close to 5 GHz, according to characteristics standardized by the International Civil Aviation Organization (ICAO), appendix 10 , paragraph 3-11.

Chacune de ces informations se décompose en deux parties, émises successivement :

  • - un préambule, dont le rôle principal est de fournir à l'aéronef une identification de l'émission qui va suivre immédiatement ; ce préambule est émis par une antenne dite sectorielle, c'est-à-dire une antenne à diagramme rayonnant fixe couvrant l'ensemble de la zone, ou secteur, couverte par le système MLS. Le préambule se présente sous la forme d'un mot binaire émis en modulation de phase différentielle DPSK (pour Differential Phase Shift. Keying en anglais), selon les normes OACI ;
  • - l'information proprement dite ; dans le cas d'une information angulaire, elle est émise à l'aide d'une antenne à balayage électronique, selon le principe connu du faisceau battant à référence temporelle (Time Référence Scanning Beam, TRSB, en anglais).
Each of these pieces of information is broken down into two parts, issued successively:
  • - a preamble, the main role of which is to provide the aircraft with an identification of the emission which will follow immediately; this preamble is issued by a so-called sectoral antenna, that is to say an antenna with a fixed radiating diagram covering the entire area, or sector, covered by the MLS system. The preamble is in the form of a binary mo t issued DPSK differential phase modulation (for Differential Phase Shift Keying in English.), According to ICAO standards;
  • - the information itself; in the case of angular information, it is transmitted using an antenna with electronic scanning, according to the known principle of the beating beam with time reference (Time Reference Scanning Beam, TRSB, in English).

La figure 1 représente une disposition fréquente des stations MLS azimut et site autour d'une piste d'atterrissage.Figure 1 shows a frequent arrangement of azimuth and site MLS stations around an airstrip.

La station azimut (AZ) est proche de l'extrémité de la piste, repérée P et d'axe ZZ. Cette station émet en direction de la piste P, permettant ainsi à l'aéronef (Ay) de disposer de l'information angulaire d'azimut durant tout l'atterrissage, et cela même durant la phase de roulement sur la piste.The azimuth station (A Z ) is close to the end of the runway, marked P and of axis ZZ. This station transmits in the direction of runway P, thus enabling the aircraft (Ay) to have the azimuth angular information during the entire landing, and this even during the taxiing phase on the runway.

La station site (S) émet dans la même direction mais elle est par contre proche du seuil d'entrée de la piste P, permettant à l'aéronef Ay d'être guidé sur une trajectoire à angle de site constant durant l'atterrissage, et d'être amené par cette trajectoire en entrée de piste.The site station (S) transmits in the same direction but it is on the other hand close to the entry threshold of runway P, allowing the aircraft Ay to be guided on a trajectory at constant site angle during the landing, and to be brought by this trajectory at the start of the runway.

De ce fait, les stations azimut et site sont généralement placées l'une par rapport à l'autre à une distance de plusieurs kilomètres.As a result, the azimuth and site stations are generally placed in relation to each other at a distance of several kilometers.

Un système MLS peut comporter d'autres stations (azimut arrière, données), non représentées sur la figure 1.An MLS system may include other stations (rear azimuth, data), not shown in Figure 1.

En outre, un système d'aide à l'atterrissage de type MLS comporte en principe un équipement de mesure de distance appelé DME (pour Distance Measuring Equipement en anglais), implanté soit dans l'une des stations MLS azimut ou site, soit à proximité de l'une d'elles. A titre d'exemple, on a représenté sur la figure 1 une station DME repérée D, placée à proximité de la station azimut AZ." La station D fournit en permanence à l'aéronef AV la distance qui le sépare de la station D (c'est-à-dire de l'extrémité de la piste P dans le cas de la figure 1), y compris dans sa phase de roulement sur la piste.In addition, a MLS type landing aid system in principle comprises distance measurement equipment called DME (for Distance Measuring Equipment in English), located either in one of the azimuth or site MLS stations, or at near one of them. By way of example, FIG. 1 shows a DME station marked D, placed near the azimuth station A Z. " Station D permanently supplies aircraft A V with the distance separating it from station D (that is to say from the end of runway P in the case of FIG. 1), including in its rolling phase on the track.

Le fonctionnement d'un système DME est le suivant : l'aéronef (AV) porte un interrogateur DME qui interroge la station au sol (D), appelée transpondeur. Le message d'interrogation est constitué par une paire d'impulsions dont l'espacement et la fréquence porteuse sont définis par les normes OACI et connus du transpondeur. Lorsque le transpondeur reçoit et reconnait ces impulsions, il émet une réponse à destination de l'aéronef. La réponse est également une paire d'impulsions, d'espacement et de fréquence porteuse connus de l'interrogateur, émises avec un retard constant et connu, le tout étant également défini par les normes OACI. Lorsque l'interrogateur de l'aéronef reçoit et reconnait ces impulsions de réponse, il déduit la distance qui le sépare de la station DME de la durée du trajet aller-retour des impulsions.The operation of a DME system is as follows: the aircraft (A V ) carries a DME interrogator which interrogates the ground station (D), called a transponder. The interrogation message consists of a pair of pulses whose spacing and carrier frequency are defined by ICAO standards and known to the transponder. When the transponder receives and recognizes these pulses, it sends a response to the aircraft. The response is also a pair of pulses, spacing and carrier frequency known to the interrogator, transmitted with a constant and known delay, the whole being also defined by the ICAO standards. When the aircraft interrogator receives and recognizes these response pulses, it deduces the distance which separates it from the DME station from the duration of the round trip of the pulses.

La station DME fonctionne, selon les normes OACI, sur une fréquence (voisine de 1 GHz) complètement distincte de celle des stations MLS (voisine de 5 GHz). Par contre, le fonctionnement en temps partagé sur une même fréquence des différentes stations MLS impose l'existence d'une liaison de synchronisation en temps entre ces stations MLS, pour assurer le non-recouvrement des émissions. En général, c'est la station azimut qui joue le rôle de station maître, mais cela n'est pas obligatoire. La station maître doit donc envoyer des signaux de synchronisation vers les autres stations MLS, dites stations esclaves, pour leur permettre d'émettre à l'instant voulu.The DME station operates, according to ICAO standards, on a frequency (close to 1 GHz) completely separate from that of the MLS stations (close to 5 GHz). On the other hand, the time-sharing operation on the same frequency of the various MLS stations requires the existence of a time synchronization link between these MLS stations, in order to ensure the non-recovery of emissions. In general, the azimuth station plays the role of master station, but this is not compulsory. The master station must therefore send synchronization signals to the other MLS stations, called slave stations, to enable them to transmit at the desired time.

Cette synchronisation de stations MLS entre elles peut être réalisée par liaison physique, câble électrique ou fibre optique par exemple. Mais elle présente alors l'inconvénient d'être onéreuse en raison des travaux de génie civil qu'elle entraîne, notamment la construction de tranchées sur des distances pouvant atteindre plusieurs kilomètres.This synchronization of MLS stations with one another can be achieved by physical link, electrical cable or optical fiber for example. However, it then has the disadvantage of being expensive because of the civil engineering work which it entails, in particular the construction of trenches over distances of up to several kilometers.

L'invention a pour objet un procédé évitant cet inconvénient par le fait qu'il assure la synchronisation radioélectriquement. Plus précisément, il assure la synchronisation d'au moins une station MLS (station esclave) par la station DME associée à une autre station du système MLS, jouant le rôle de station maître, selon le procédé tel que défini par la revendication 1.The invention relates to a method avoiding this drawback by the fact that it ensures radio synchronization. More specifically, it ensures the synchronization of at least one MLS station (slave station) by the DME station associated with another station of the MLS system, playing the role of master station, according to the method such as defined by claim 1.

Elle a également pour objet une station DME et un récepteur de type DME pour la mise en oeuvre de ce procédé, tel que défini respectivement par les revendications 5 et 6.It also relates to a DME station and a DME type receiver for implementing this method, as defined by claims 5 and 6 respectively.

D'autres objets, particularités et résultats de l'invention ressortiront de la description qui suit, illustrée par les dessins annexés qui représentent :

  • - la figure 1, le schéma général d'implantation et d'émission des stations MLS et DME ;
  • - la figure 2, le schéma général d'une station MLS émettant une fonction angulaire ;
  • - la figure 3, le schéma général d'une station DME (transpondeur) ;
  • - les figures 4, a à c, des modes de réalisation de la station DME (transpondeur) utilisée dans le procédé selon l'invention, et des diagrammes de signaux s'y rapportant ;
  • - la figure 5, un mode de réalisation d'un récepteur de type DME associé à une station MLS esclave, utilisé dans le procédé selon l'invention.
Other objects, features and results of the invention will emerge from the description which follows, illustrated by the appended drawings which represent:
  • - Figure 1, the general layout and transmission diagram of the MLS and DME stations;
  • - Figure 2, the general diagram of an MLS station transmitting an angular function;
  • - Figure 3, the general diagram of a DME station (transponder);
  • - Figures 4, a to c, embodiments of the DME station (transponder) used in the method according to the invention, and signal diagrams relating thereto;
  • - Figure 5, an embodiment of a DME type receiver associated with a slave MLS station, used in the method according to the invention.

Sur ces différentes figures, les mêmes références se rapportent aux mêmes éléments.In these different figures, the same references relate to the same elements.

La figure 1 représente donc l'organisation générale du système MLS-DME, synchronisé selon l'invention.FIG. 1 therefore represents the general organization of the MLS-DME system, synchronized according to the invention.

Outre les éléments déjà décrits, à savoir la piste P, les stations MLS azimut AZ et site S et la station DME (transpondeur) D, le système selon l'invention comporte en outre une station réceptrice DS de type DME, implantée dans la station esclave (site) ou à proximité de celle-ci.In addition to the elements already described, namely the track P, the azimuth MLS stations A Z and site S and the DME station (transponder) D, the system according to the invention furthermore comprises a DME type DME receiving station, located in the slave station (site) or close to it.

On a représenté par une flèche dD l'émission DME classique du transpondeur D vers l'aéronef AV, et par une flèche dA l'émission inverse.There is shown by an arrow d D the conventional DME transmission from the transponder D to the aircraft A V , and by an arrow dA the reverse transmission.

Selon l'invention, pour synchroniser une ou plusieurs stations MLS esclaves sur une station MLS maître, la station DME D émet en outre une information de synchronisation, appelée SYD, à l'intention d'un récepteur de type DME, noté DS et situé dans chacune des stations MLS esclaves ou à proximité de celles-ci ; dans l'exemple de la figure 1, il n'y a qu'une station esclave, la station site S, et cette émission est représentée par une flèche dS. Cette émission de synchronisation se fait sur commande, notée SYA, de la station MLS maître (la station azimut). La station DME D étant placée dans l'exemple de la figure 1 à proximité de la station azimut, mais non à l'intérieur de celle-ci, il doit être réalisé une liaison entre ces deux stations, par câble de préférence. A l'autre extrémité de la piste, le récepteur DME DS étant placé (toujours dans l'exemple de la figure 1) à proximité de la station site, c'est-à-dire à une distance de l'ordre de quelques mètres, la liaison nécessaire entre les deux stations se fait également de préférence par câble. L'information de synchronisation reçue par le récepteur DME DS et transmise à la station MLS S est notée SYS' According to the invention, in order to synchronize one or more slave MLS stations with a master MLS station, the DME station D also transmits synchronization information, called S YD , intended for a DME type receiver, denoted D S and located in or near each of the slave MLS stations; in the example of FIG. 1, there is only one slave station, the site station S, and this transmission is represented by an arrow d S. This synchronization transmission is made on command, denoted S YA , from the master MLS station (the azimuth station). The DME station D being placed in the example of FIG. 1 near the azimuth station, but not inside the latter, a connection must be made between these two stations, preferably by cable. At the other end of the runway, the DME D S receiver being placed (still in the example in FIG. 1) near the site station, that is to say at a distance of the order of a few meters, the necessary connection between the two stations is also preferably by cable. The synchronization information received by the receiver DME D S and transmitted to the station MLS S is noted S YS '

Il est à noter que l'impulsion de synchronisation doit être émise par la station maître un temps (T) suffisant avant l'instant d'émission de la station esclave, le temps T étant défini par T=TD+TC+TP,avec:

  • - TD: temps de propagation entre les stations DME (D) et MLS esclave (S),
  • - TC : durée de l'information de sychronisation codée,
  • - Tp : temps de protection de synchronisation, pendant lequel il n'est procédé à aucune autre émission (de l'ordre de ±10 us).
It should be noted that the synchronization pulse must be transmitted by the master station a sufficient time (T) before the instant of transmission from the slave station, the time T being defined by T = T D + T C + T P , with:
  • - T D : propagation time between DME (D) and MLS slave (S) stations,
  • - T C : duration of the coded synchronization information,
  • - Tp: synchronization protection time, during which no other transmission takes place (of the order of ± 10 us).

Selon une variante de réalisation de l'invention, la station MLS esclave (station site) transmet en outre l'état E de fonctionnement ou de non fonctionnement dans lequel elle se trouve à la station maître (station azimut), cette transmission se faisant également par l'intermédiaire de la station DME comme représenté par les flèches en pointillés sur la figure 1 : par câble, la station site S transmet son état E à la station DME D S, laquelle transmet cette information à la station DME D par la voie radioélectrique (flèche dE) ; à réception de cette information d'état, la station DME D la transmet à la station azimut AZ par câble également.According to an alternative embodiment of the invention, the slave MLS station (site station) also transmits the operating or non-operating state E in which it is located to the master station (azimuth station), this transmission also taking place by via the DME station as shown by the dotted arrows in FIG. 1: by cable, the site station S transmits its status E to the DME station D S , which transmits this information to the DME D station by radio (arrow d E ); on receipt of this status information, the DME station D transmits it to the azimuth station A Z also by cable.

Afin de réaliser ces différentes fonctions, le système selon l'invention utilise donc un transpondeur DME (D) de type classique, auquel on rajoute un codeur particulier adapté à l'émission de l'information de synchronisation SYD et, le cas échéant, un décodeur particulier pour la réception de l'information d'état E, et au moins une station supplémentaire de type DME, implantée à proximité de la ou des stations MLS esclaves, comportant principalement un récepteur et un décodeur de l'information de synchronisation, auxquels s'ajoutent de préférence une horloge locale et un système d'asservissement de cette horloge sur l'horloge de la station maître et, le cas échéant, un ensemble d'émission de l'information d'état E de la station esclave. Avant de décrire ces différentes stations DME dans leur utilisation à la synchronisation (figures 3 à 5), on décrit ci-après plus en détails le système MLS.In order to carry out these various functions, the system according to the invention therefore uses a DME (D) transponder of the conventional type, to which a particular coder adapted to the transmission of the synchronization information S YD is added and, if necessary, a particular decoder for receiving state information E, and at least one additional DME type station, located near the slave MLS station (s), mainly comprising a receiver and a decoder for synchronization information, to which are preferably added a local clock and a system for controlling this clock on the clock of the master station and, where appropriate, a set of transmitting state information E of the slave station. Before describing these different DME stations in their use at synchronization (FIGS. 3 to 5), the MLS system is described below in more detail.

La figure 2 est un schéma de l'organisation générale classique d'une station angle d'un système MLS, azimut ou site par exemple.FIG. 2 is a diagram of the conventional general organization of an angle station of an MLS system, azimuth or site for example.

Cette station comporte essentiellement un émetteur 1, deux antennes : une antenne sectorielle 3 et une antenne à balayage électronique 4, et des circuits de commande (2, 5).This station essentially comprises a transmitter 1, two antennas: a sectoral antenna 3 and an antenna with electronic scanning 4, and control circuits (2, 5).

L'émetteur 1 comporte classiquement, en cascade :

  • - un générateur de fréquence, constitué par exemple par un synthétiseur de fréquence fournissant une onde voisine de 5 GHz selon la norme OACI (on rappelle que, selon cette norme, une fréquence parmi 200 fréquences prédéfinies, voisine de 5 GHz, est affectée à chaque station MLS) ;
  • - un modulateur de phase, réalisant une modulation de phase DPSK à deux états (O,π) permettant d'émettre le préambule et les données sur commande d'un dispositif logique de commande 5, tel qu'un microprocesseur ;
  • - un dispositif de commande marche/arrêt, également commandé par le microprocesseur 5 ;
  • - un émetteur de puissance, réalisé à l'aide de tubes ou de transistors selon la puissance requise, qui est classiquement de l'ordre de 20W et donc le plus souvent réalisé à l'aide de transistors.
The transmitter 1 conventionally comprises, in cascade:
  • a frequency generator, constituted for example by a frequency synthesizer providing a wave close to 5 GHz according to the ICAO standard (it is recalled that, according to this standard, a frequency among 200 predefined frequencies, close to 5 GHz, is assigned to each MLS station);
  • - a phase modulator, performing phase modulation DPSK with two states (O, π) for transmitting the preamble and the data on command from a logic control device 5, such as a microprocessor;
  • - an on / off control device, also controlled by the microprocessor 5;
  • - A power transmitter, produced using tubes or transistors according to the required power, which is conventionally of the order of 20W and therefore most often produced using transistors.

L'émetteur 1 fournit un signal, par l'intermédiaire d'un commutateur 2, soit à l'antenne sectorielle 3 pour l'émission du préambule et des données, de base ou auxiliaires, soit à l'antenne à balayage 4.The transmitter 1 supplies a signal, via a switch 2, either to the sectoral antenna 3 for the transmission of the preamble and the data, basic or auxiliary, or to the scanning antenna 4.

Cette dernière (4) se décompose, classiquement, en un diviseur (ou répartiteur) de puissance, divisant la puissance reçue du commutateur 2 en N afin d'alimenter N déphaseurs numériques, lesquels alimentent N éléments rayonnants ; les valeurs des déphasages introduits par les déphaseurs sont commandées par un circuit logique de balayage, afin de réaliser un balayage électronique à partir d'éléments rayonnants statiques.The latter (4) is conventionally broken down into a power divider (or distributor), dividing the power received from switch 2 into N in order to supply N digital phase shifters, which supply N radiating elements; the values of the phase shifts introduced by the phase shifters are controlled by a scanning logic circuit, in order to carry out an electronic scanning from static radiating elements.

L'ensemble de la station est donc commandée par le microprocesseur 5 et sa mémoire, connecté à l'émetteur 1, au commutateur 2 et à l'antenne à balayage 4, par l'intermédiaire de son circuit logique de balayage, le microprocesseur 5 fournissant au circuit logique de balayage l'instant de départ du balayage pour les fonctions angle. En outre, dans le cas de la station maître, le microprocesseur 5 fournit (flèche 50) le signal de synchronisation SYA à la station DME D. Dans le cas d'une station esclave, il fournit; le cas échéant, une information E sur l'état de la station à la station DME DS.The entire station is therefore controlled by the microprocessor 5 and its memory, connected to the transmitter 1, to the switch 2 and to the scanning antenna 4, by means of its scanning logic circuit, the microprocessor 5 providing the scanning logic circuit with the start time of the scanning for the angle functions. In addition, in the case of the master station, the microprocessor 5 supplies (arrow 50) the synchronization signal S YA to the DME station D. In the case of a slave station, it supplies; if necessary, information E on the state of the station at the station DME D S.

Plus précisément, selon un mode de réalisation, on définit dans le microprocesseur 5 un "mot d'état" de là station, chaque bit de ce mot représentant une commande ; dans l'exemple ci-dessus, ce mot comporte au moins six bits, commandant respectivement :

  • -le modulateur et le dispositif de commande de l'émetteur 1 ;
  • - le commutateur 2
  • - la logique de balayage de l'antenne 4 (2 bits) ;
  • - la synchronisation de la station esclave, dans le cas de la station maître.
More precisely, according to one embodiment, a microprocessor 5 defines a "status word" from the station, each bit of this word representing a command; in the example above, this word comprises at least six bits, respectively controlling:
  • the modulator and the control device of the transmitter 1;
  • - switch 2
  • - the antenna scanning logic 4 (2 bits);
  • - synchronization of the slave station, in the case of the master station.

Chacune des stations MLS émet donc à tour de rôle selon un séquencement prédéfini et périodique, normalisé par l'OACI, appelé cycle et dont la durée est de 615 ms.Each of the MLS stations therefore transmits in turn according to a predefined and periodic sequencing, standardized by the ICAO, called cycle and whose duration is 615 ms.

La génération en temps réel d'un cycle MLS revient à engendrer en temps réel le mot d'état dans le microprocesseur, qui réalise ensuite les différentes commandes. A cet effet, on range dans une table de la mémoire du microproccesseur 5 la succession des mots d'état correspondant au cycle désiré. Au rythme d'une horloge convenable, le microprocesseur 5 va chercher les mots d'état successifs et les fournit à une interface (non représentée), du type PIA (pour "Parallel Interface Adapter") par exemple, qui commande les divers blocs de la station MLS.Generating an MLS cycle in real time means generating the status word in real time in the microprocessor, which then performs the various commands. To this end, the succession of status words corresponding to the desired cycle is stored in a table in the memory of the microprocessor 5. At the rhythm of a suitable clock, the microprocessor 5 will seek the successive state words and supply them to an interface (not shown), of the PIA type (for "Parallel Interface Adapter") for example, which controls the various blocks of MLS station.

La figure 3 représente le schéma général d'un transpondeur D de type DME.FIG. 3 represents the general diagram of a DME D type transponder.

Un tel transpondeur comporte une antenne AD, susceptible d'émettre et recevoir des émissions DME sur les fréquences normalisées, voisines de 1 MHz ; elle est reliée à un diplexeur DI, dont la fonction est, ainsi qu'il est connu, d'assurer la liaison de l'antenne AD alternativement avec un récepteur RX et un émetteur TX du transpondeur D. Le récepteur Rx a pour fonction d'amplifier et de détecter les impulsions dans les signaux reçus par l'antenne AD, ainsi que de décoder ces signaux, c'est-à-dire de ne prendre en considération que ceux qui ont pour fréquence porteuse la fréquence DME affectée au transpondeur considéré et que les paires d'impulsions dont l'espacement correspond à l'espacement DME normalisé.Such a transponder comprises an antenna A D , capable of transmitting and receiving DME transmissions on the standardized frequencies, close to 1 MHz; it is connected to a diplexer D I , the function of which, as is known, is to provide the connection of the antenna A D alternately with a receiver R X and a transmitter T X of the transponder D. The receiver R x has the function of amplifying and detecting the pulses in the signals received by the antenna A D , as well as of decoding these signals, that is to say of taking into consideration only those which have as carrier frequency the DME frequency assigned to the transponder in question and that the pairs of pulses whose spacing corresponds to the normalized DME spacing.

Losque un signal reçu a été reconnu par le récepteur RX comme des impulsions d'interrogation DME, le transpondeur doit élaborer une réponse, constituée elle aussi par deux impulsions émises à une fréquence déterminée et espacées d'un intervalle de temps déterminé. Ces impulsions de réponse sont élaborées dans un codeur C, sur commande du récepteur RX. Elles sont transmises à l'émetteur TX pour émission par l'antenne AD via le diplexeur Dr When a received signal has been recognized by the receiver R X as DME interrogation pulses, the transponder must develop a response, also consisting of two pulses transmitted at a determined frequency and spaced apart by a determined time interval. These response pulses are developed in a encoder C, on command of receiver R X. They are transmitted to the transmitter T X for transmission by the antenna AD via the diplexer D r

L'émetteur TX et le récepteur RX sont pilotés par un oscillateur local Op, qui fournit à l'émetteur TX la fréquence d'émission du transpondeur (voisine de 1 GHz) et au récepteur RX la fréquence nécessaire au changement de fréquence (on rappelle que si la fréquence d'émission du transpondeur est égale à Fo, la fréquence d'émission de l'interrogateur de l'aéronef est égale à F o + 63 MHz).The transmitter T X and the receiver R X are controlled by a local oscillator Op, which supplies the transmitter T X with the transmission frequency of the transponder (around 1 GHz) and the receiver R X with the frequency necessary for changing frequency (it is recalled that if the transponder transmission frequency is equal to F o , the aircraft interrogator transmission frequency is equal to F o + 63 MH z ).

Selon l'invention, le transpondeur D a également pour fonction d'émettre une information de synchronisation (SYD) à destination du récepteur DME DS (figure 1). A cet effet, il reçoit de la station azimut AZ un signal de synchronisation SYA qui, appliqué au codeur C, déclenche par celui-ci l'émission de l'information de synchronisation sous forme d'impulsions, dont le nombre et l'espacement sont choisis pour être distincts des impulsions DME classiques. Les impulsions de synchronisation élaborées par le codeur C sont ensuite transmises à l'émetteur TX puis à l'antenne AD comme les impulsions classiques.According to the invention, the transponder D also has the function of transmitting synchronization information (S YD ) to the DME receiver D S (FIG. 1). To this end, it receives from the azimuth station A Z a synchronization signal S YA which, applied to the encoder C, triggers by the latter the emission of the synchronization information in the form of pulses, the number and l spacing are chosen to be distinct from conventional DME pulses. The synchronization pulses produced by the encoder C are then transmitted to the transmitter T X and then to the antenna A D like the conventional pulses.

On rappelle que les normes OACI définissent 200 canaux MLS "angle", situés entre 5031 MHz et 5090,7 MHz, espacés de 300 KHz. A chaque canal "angle" est associé un canal DME, défini par sa fréquence (entre 962 et 1150 MHz par pas de 1 MHz) et son code, c'est-à-dire l'espacement entre deux impulsions d'une paire (quatre codes distincts entre 12 et 42 us, la largeur de l'impulsion DME à mi-hauteur étant de 3,5 µs).It is recalled that the ICAO standards define 200 MLS "angle" channels, located between 5031 MHz and 5090.7 MHz, spaced 300 KHz apart. Each DME channel is associated with a DME channel, defined by its frequency (between 962 and 1150 MHz in steps of 1 MHz) and its code, that is to say the spacing between two pulses of a pair ( four separate codes between 12 and 42 us, the width of the DME pulse at mid-height being 3.5 µs).

L'information de synchronisation est émise sur la fréquence de réponse affectée au transpondeur considéré, sous forme d'au moins deux impulsions, avec un code différent de ceux qui sont utilisés par le DME. En pratique, pour réduire la probabilité d'avoir de fausses informations de synchronisation dues à l'émission des paires d'impulsions DME, il est préférable d'utiliser trois impulsions, ou davantage, mais le nombre de trois constitue un bon optimum entre sécurité et simplicité. En outre, dans le même esprit, il est préférable d'utiliser des espacements entre impulsions supérieurs à l'espacement DME maximum, à savoir 42 µs. Une autre possibilité consiste à utiliser des espacements plus courts, mais avec un plus grand nombre d'impulsions.Synchronization information is sent on the response frequency assigned to the transponder in question, in the form of at least two pulses, with a code different from those used by the DME. In practice, to reduce the probability of having false synchronization information due to the emission of pairs of DME pulses, it is preferable to use three or more pulses, but the number of three constitutes a good optimum between safety. and simplicity. In addition, in the same spirit, it is better to use spacings between pulses greater than the maximum DME spacing, namely 42 µs. Another possibility is to use shorter spacings, but with more pulses.

La figure 4a est le schéma d'un mode de réalisation du dispositif de codage C selon l'invention, assurant la génération à la fois des impulsions de réponse classiques du transpondeur DME et des impulsions de synchronisation.FIG. 4a is the diagram of an embodiment of the coding device C according to the invention, ensuring the generation of both conventional response pulses from the DME transponder and synchronization pulses.

Le dispositif C comporte donc un codeur CD élaborant la réponse classique d'un transpondeur DME, recevant un ordre d'émission du récepteur RX et transmettant les impulsions qu'il a élaborées à l'émetteur TX, et plus précisément au modulateur qu'il comporte par l'intermédiaire d'un circuit logique CL. Le dispositif C comporte un second codeur CSY qui a pour fonction, sur réception du signal de synchronisation SYA en provenance de la station azimut AZ, d'engendrer les impulsions de synchronisation à destination de l'émetteur TX, via le circuit logique CL qui permet d'éviter tout conflit d'accès à l'émetteur TX entre les deux codeurs CD et CSY. Le codeur CSY peut avantageusement être réalisé comme le codeur CD, lequel, classiquement, est réalisé à partir d'un registre à décalage ou d'un compteur.The device C therefore comprises an encoder C D developing the conventional response of a DME transponder, receiving an emission command from the receiver R X and transmitting the pulses which it has produced to the transmitter T X , and more precisely to the modulator that it comprises by means of a logic circuit C L. The device C comprises a second encoder C SY which has the function, on reception of the synchronization signal S YA coming from the azimuth station A Z , of generating the synchronization pulses intended for the transmitter T X , via the circuit logic C L which makes it possible to avoid any conflict of access to the transmitter T X between the two coders CD and C SY . The coder C SY can advantageously be produced like the coder C D , which, conventionally, is produced from a shift register or a counter.

La figure 4b, représente un mode de réalisation du circuit logique C L.FIG. 4b represents an embodiment of the logic circuit C L.

Dans ce mode de réalisation, le circuit CL comporte : deux portes logiques, l'une du type ET repérée 11 et l'autre du type OU non exclusif repérée 12 ; un circuit 13 tel qu'un monostable, permettant d'engendrer un signal assurant la priorité des informations de synchronisation sur les informations en provenance du codeur CD ; un inverseur 15 placé en sortie du circuit 13, et un circuit 14, tel qu'un monostable, connecté entre les codeur CSY et la porte OU 12.In this embodiment, the circuit C L comprises: two logic gates, one of the AND type marked 11 and the other of the non-exclusive OR type marked 12; a circuit 13 such as a monostable, making it possible to generate a signal ensuring the priority of the synchronization information over the information coming from the encoder C D ; an inverter 15 placed at the output of circuit 13, and a circuit 14, such as a monostable, connected between the encoders C SY and the OR gate 12.

Le fonctionnement de ce circuit est le suivant, illustré par les diagrammes de la figure 4c : sur commande de l'impulsion de synchronisation SYA, représentée sur la première ligne de la figure 4c, le codeur de synchronisation CSY engendre une série d'impulsions représentant l'information de synchronisation ; trois de ces impulsions sont représentées à titre d'exemple sur la deuxième ligne de la figure 4c. Ces impulsions sont appliquées d'une part au circuit 13 et d'autre part à une entrée de la porte OU 12, par l'intermédiaire du monostable 14. En présence d'informations de synchronisation à transmettre, les dispositifs 13 et 15 engendrent des signaux (représentés figure 4c à la sortie du circuit 13) tels qu'ils inhibent, par l'intermédiaire de la porte ET 11, le passage des signaux en provenance du codeur CD ; les signaux de synchronisation passent alors par la porte OU 12, par l'intermédiaire du monostable 14. En l'absence d'information de synchronisation, les informations en provenance du codeur CD parviennent à l'émetteur TX par l'intermédiaire successivement des portes ET 11 et OU 12. La fonction du circuit 14 est de conférer un retard aux impulsions de synchronisation issues du codeur CSY, comme représenté sur la dernière ligne de la figure 4c, afin d'éviter toute coïncidence avec une impulsion DME en provenance du codeur CD ; la valeur du retard ainsi conféré, de l'ordre de 10 µs, constitue le temps de protection de synchronisation Tp mentionné plus haut.The operation of this circuit is as follows, illustrated by the diagrams in Figure 4c: on command of the pulse synchronization S YA , represented on the first line of FIG. 4c, the synchronization coder C SY generates a series of pulses representing the synchronization information; three of these pulses are shown by way of example in the second line of FIG. 4c. These pulses are applied on the one hand to the circuit 13 and on the other hand to an input of the OR gate 12, via the monostable 14. In the presence of synchronization information to be transmitted, the devices 13 and 15 generate signals (shown in Figure 4c at the output of circuit 13) such that they inhibit, through the AND gate 11, the passage of signals from the encoder C D ; the synchronization signals then pass through the OR gate 12, via the monostable 14. In the absence of synchronization information, the information coming from the encoder C D reaches the transmitter T X by successively AND gates 11 and OR 12. The function of circuit 14 is to give a delay to the synchronization pulses coming from the encoder C SY , as shown on the last line of FIG. 4c, in order to avoid any coincidence with a DME pulse in origin of coder C D ; the value of the delay thus conferred, of the order of 10 μs, constitutes the synchronization protection time Tp mentioned above.

La figure 5 représente le schéma d'un mode de réalisation du récepteur DME DS utilisé pour la synchronisation d'une station MLS esclave.FIG. 5 represents the diagram of an embodiment of the DME D S receiver used for the synchronization of a slave MLS station.

Ce récepteur DS comporte les éléments classiques d'un récepteur DME, à savoir : une antenne repérée AS et un récepteur, détecteur et décodeur RXS, piloté par un oscillateur local OpS. Il comporte en outre un dispositif 30, appelé séquenceur MLS ; la fonction de ce séquenceur 30 est de dérouler le cycle MLS à partir de la réception des informations de synchronisation ; il est réalisé par exemple à l'aide d'un microprocesseur et fournit l'information de synchronisation SYS à la station MLS esclave, la station site S dans cet exemple, information de synchronisation qui déclenchera l'émission de la fonction MLS par la station esclave.This receiver D S comprises the conventional elements of a DME receiver, namely: an antenna marked A S and a receiver, detector and decoder R XS , controlled by a local oscillator Op S. It further comprises a device 30, called an MLS sequencer; the function of this sequencer 30 is to run the MLS cycle from the reception of the synchronization information; it is produced for example using a microprocessor and provides synchronization information S YS to the slave MLS station, the site station S in this example, synchronization information which will trigger the transmission of the MLS function by the slave station.

L'antenne AS est une antenne directive, orientée vers la station DME D et susceptible de recevoir ses émissions. Le récepteur RXS a pour fonction d'amplifier, de détecter les signaux reçus par l'antenne AS et de décoder et reconnaître les impulsions reçues afin de fournir une impulsion de synchronisation Sm à chaque fois que la suite d'impulsions de synchronisation attendue est reçue de la station maître, via la station DME. Dans un mode de réalisation (non représenté), l'impulsion Sm est directement utilisée pour le déclenchement du séquenceur MLS 30.The antenna A S is a directive antenna, oriented towards the DME D station and capable of receiving its emissions. The function of the receiver R XS is to amplify, to detect the signals received by the antenna A S and to decode and recognize the pulses received in order to supply a synchronization pulse S m each time the series of synchronization pulses expected is received from the master station, via the DME station. In one embodiment (not shown), the pulse S m is used directly for triggering the MLS 30 sequencer.

Dans un mode de réalisation préféré, illustré sur la figure 5, le récepteur DS comporte en outre une horloge H et un ensemble de circuits électroniques 20 à 29 destinés à engendrer, à partir de la période de l'horloge H, un signal de synchronisation au début de chaque cycle MLS, ainsi qu'à asservir cette horloge H sur le signal de synchronisation reçu par le récepteur RXS.In a preferred embodiment, illustrated in FIG. 5, the receiver D S further comprises a clock H and a set of electronic circuits 20 to 29 intended to generate, from the period of the clock H, a signal of synchronization at the start of each MLS cycle, as well as to control this clock H on the synchronization signal received by the receiver R XS .

Afin d'engendrer le signal de synchronisation de la station esclave, noté SE, la fréquence de l'horloge locale H est divisée par un nombre N à l'aide d'un dispositif 20, réalisé par exemple par un compteur, afin de fournir une impulsion de synchronisation par périodes de 615 ms qui est, on le rappelle, la durée normalisée du cycle MLS.In order to generate the synchronization signal from the slave station, denoted S E , the frequency of the local clock H is divided by a number N using a device 20, produced for example by a counter, in order to provide a synchronization pulse in periods of 615 ms which is, as we recall, the normalized duration of the MLS cycle.

L'asservissement de la référence de temps de la station DS est réalisé à la fois pour les dérives à court terme et pour les dérives à long terme.The time reference of the station D S is controlled both for short-term drifts and for long-term drifts.

La correction des dérives à court terme est réalisée en remettant à zéro (entrée RAZ) le compteur 20 par le signal de synchronisation SM.The correction of short-term drifts is carried out by resetting (reset input) the counter 20 by the synchronization signal S M.

La correction des dérives à long terme de l'horloge H est effectuée en modifiant le rang de division du compteur 20 d'une valeur égale à ± An à l'aide des circuits 21 à 29, qui reçoivent les signaux SM et SE.The correction of the long-term drifts of the clock H is carried out by modifying the division rank of the counter 20 by a value equal to ± An using the circuits 21 to 29, which receive the signals S M and S E .

Plus précisément, ces circuits comportent une bascule 24, du type RS, dont les entrées R et S reçoivent les signaux SM et SE par l'intermédiaire de deux portes ET, respectivement 26 et 25. Entre les entrées des portes ET 25 et 26 et les signaux Sm et SE sont connectés :

  • - un monostable 27 entre le signal SM et l'une des entrées de la porte 25 ;
  • - un élément à retard 29 entre le signal SE et la deuxième entrée de la porte 25 ;
  • - un monostable 28 entre la sortie de l'élément à retard 29 et la première entrée de la porte 26, la deuxième entrée de cette même porte recevant directement le signal SM.
More precisely, these circuits include a flip-flop 24, of the RS type, the inputs R and S of which receive the signals S M and SE via two AND gates, respectively 26 and 25. Between the inputs of AND gates 25 and 26 and the signals S m and SE are connected:
  • - a monostable 27 between the signal S M and one of the inputs of the door 25;
  • - A delay element 29 between the signal SE and the second input of the gate 25;
  • a monostable 28 between the output of the delay element 29 and the first input of the door 26, the second input of this same door directly receiving the signal S M.

Avant la réception d'une impulsion de synchronisation, les deux monostables 27 et 28 sont au repos, leur sortie étant au niveau 1.Before receiving a synchronization pulse, the two monostables 27 and 28 are at rest, their output being at level 1.

Lorsque le signal de synchronisation SE apparaît avant le signal de synchronisation SM en provenance de la station maître, le signal SE passe la porte ET 25 et se présente à l'entrée S de la bascule 24. La sortie Q de cette bascule est reliée à une entrée de sélection (comptage ou décomptage) d'un compteur-décompteur 22 ; dans le cas présent, elle positionne le dispositif 22 de sorte qu'il compte vers les nombres croissants lorsqu'il reçoit une impulsion venant d'un monostable 23, lequel reçoit le signal SM. Lorsque ce dernier signal est reçu par le monostable 23, il provoque donc l'accroissement d'une unité de la valeur initiale n du compteur 22. Parallèlement, la présence du signal SE sur l'entrée du monostable 28 change l'état de sortie de ce dernier (qui passe au niveau 0) et interdit ainsi le passage de l'impulsion SM par la porte ET 26 : le signal SM, arrivé dans cette hypothèse après le signal SE, ne peut avoir ainsi d'effet sur la bascule 24. A la sortie du compteur-décompteur 22, un circuit mémoire 21 mémorise la valeur N = no ±Δn
contenue dans le compteur 22 et positionne le diviseur 20 à la valeur N. Le rang de la division, dans l'exemple de fonctionnement décrit, s'étant accru d'une unité (An = 1), la période du signal SE devient plus longue et, à chaque fois que le signal SE arrive avant le signal SM, le contenu du compteur 12 est ainsi augmenté d'une unité.When the synchronization signal SE appears before the synchronization signal S M from the master station, the signal SE passes through the AND gate 25 and occurs at the input S of the flip-flop 24. The output Q of this flip-flop is connected to a selection input (up or down) of an up-down counter 22; in the present case, it positions the device 22 so that it counts towards the increasing numbers when it receives a pulse coming from a monostable 23, which receives the signal S M. When the latter signal is received by the monostable 23, it therefore causes the initial value n of the counter 22 to increase by one unit. At the same time, the presence of the signal SE on the input of the monostable 28 changes the output state. of the latter (which goes to level 0) and thus prohibits the passage of the pulse S M through the gate AND 26: the signal S M , arrived in this hypothesis after the signal SE, can thus have no effect on the flip-flop 24. At the output of the up-down counter 22, a memory circuit 21 stores the value N = n o ± Δn
contained in the counter 22 and positions the divider 20 at the value N. The division rank, in the operating example described, having increased by one unit (An = 1), the period of the signal SE becomes longer long and, each time the signal SE arrives before the signal S M , the content of the counter 12 is thus increased by one.

Lorsque la période SE devient égale ou supérieure à celle du signal SM, un processus inverse s'établit et, par l'intermédiaire de la porte ET 26 et de l'entrée R de la bascule 24, le compteur-décompteur 22 décompte une unité à chaque fois que le signal Sm arrive avant le signal SE.When the SE period becomes equal to or greater than that of signal S M , an inverse process is established and, via the AND gate 26 and the input R of the flip-flop 24, the up-down counter 22 counts down one unit each time the signal S m arrives before the SE signal.

La fonction du circuit de retard 29 est la suivante : du fait que le signal Sm remet à zéro le compteur 21 chaque fois qu'il est présent, une impulsion de sortie étant produite par ce compteur à chaque fois que son contenu est égal à zéro, il y aurait un signal SE à chaque fois qu'un signal Sm est présent ; le circuit à retard 29, qui introduit un retard de l'ordre de quelques centaines de nano-secondes, considéré comme négligeable par rapport aux durées Tp et TC, permet d'assurer l'avance du signal SM sur le signal SE.The function of the delay circuit 29 is as follows: the fact that the signal S m resets the counter 21 to zero each time it is present, an output pulse being produced by this counter each time its content is equal to zero, there would be a signal SE whenever a signal S m is present; the delay circuit 29, which introduces a delay of the order of a few hundred nanoseconds, considered to be negligible compared to the durations Tp and T C , makes it possible to ensure the advance of the signal S M over the signal SE.

On constate ainsi qu'en l'absence du signal de synchronisation SM émanant de la station maître, le compteur-décompteur 22, ne recevant pas d'impulsion du monostable 23, conserve son état et, par suite, le diviseur 20 conserve également son rang de division N =no ± Δn établi avant la disparition du signal SM.It can thus be seen that in the absence of the synchronization signal S M emanating from the master station, the up-down counter 22, not receiving a pulse from the monostable 23, retains its state and, consequently, the divider 20 also retains its division rank N = n o ± Δn established before the disappearance of the signal S M.

Dans une variante de réalisation, un autre compteur, repéré 31, est utilisé pour compter le temps d'autonomie de la station DS : il arrête l'émission de la station esclave lorsque celle-ci ne reçoit plus l'impulsion de synchronisation SM pendant un intervalle de temps prédéfini, et il est remis à zéro à chaque fois qu'une impulsion SM est reçue. Dans une variante de réalisation, le compteur 31 peut également fournir un signal de préalarme sur une valeur intermédiaire de son contenu.In an alternative embodiment, another counter, marked 31, is used to count the autonomy time of the station D S : it stops the transmission from the slave station when the latter no longer receives the synchronization pulse S M during a predefined time interval, and it is reset to zero each time an S M pulse is received. In an alternative embodiment, the counter 31 can also provide a pre-alarm signal on an intermediate value of its content.

Dans la variante de réalisation décrite figure 1 dans laquelle la station esclave, site par exemple, transmet une information sur son état à la station DME DS, laquelle la retransmet à la station DME D de façon radioélectrique, à destination de la station maître AZ, la station DME DS doit alors inclure en outre, de façon analogue à ce qui est représenté sur la figure 3, un circuit de codage codant l'information d'état de la station esclave selon un code spécifique, c'est-à-dire sous forme d'une série d'impulsions dont l'espacement est distinct des précédents, et un émetteur de cette information codée, à la fréquence d'interrogation affectée à la station DME considérée, et la transmettant à l'antenne AS de la station DS par l'intermédiaire d'un diplexeur. Dans ce cas, la station DME D doit en outre comporter un décodeur adapté pour reconnaître l'information d'état de la station esclave.In the alternative embodiment described in FIG. 1 in which the slave station, site for example, transmits information on its state to the DME D S station , which retransmits it to the DME D station by radio, intended for the master station A Z , the DME station D S must then also include, analogously to what is shown in FIG. 3, a coding circuit coding the status information of the slave station according to a specific code, that is to say ie in the form of a series of pulses whose spacing is distinct from the previous ones, and a transmitter of this information coded, at the interrogation frequency assigned to the DME station considered, and transmitting it to the antenna A S of the station D S via a diplexer. In this case, the DME D station must also include a decoder adapted to recognize the status information of the slave station.

On a ainsi décrit un procédé de synchronisation de stations MLS utilisant la station DME qui leur est associée. Un avantage de ce mode de synchronisation, outre les avantages déjà décrits, tient au fait que les impulsions normalisées engendrées par les stations DME ont des fronts raides, ce qui confère une grande précision à la synchronisation.We have thus described a method for synchronizing MLS stations using the DME station associated with them. An advantage of this synchronization mode, in addition to the advantages already described, is due to the fact that the normalized pulses generated by the DME stations have steep edges, which gives great precision to synchronization.

La description faite ci-dessus ne l'a été bien entendu qu'à titre d'exemple non limitatif. C'est ainsi notamment que peuvent être transmises entre les stations MLS et l'extérieur, via la station DME, d'autres informations que la synchronisation ou des informations d'état, comme la télécommande ou le télécontrôle des stations MLS à partir de la tour de contrôle de l'aéroport, à condition d'ajouter les émetteurs et récepteurs du type DME aux endroits nécessaires.The description given above has obviously been understood by way of non-limiting example. Thus, in particular, information can be transmitted between the MLS stations and outside via the DME station, other than synchronization or status information, such as the remote control or the remote control of the MLS stations from the airport control tower, provided that DME transmitters and receivers are added where necessary.

Claims (10)

1. Procédé de synchronisation radioélectrique d'au moins deux stations d'un système d'aide à l'atterrissage de type MLS, l'une des stations, dite station MLS maître, fournissant une information de synchronisation à l'intention de l'autre station, dite station MLS esclave, ledit procédé étant caractérisé par le fait qu'il comporte : - une étape de transmission de l'information de synchronisation (SYA) de la station MLS maître (A Z) à une station de type DME (D) qui lui est associée ; - une étape d'émission radioélectrique, par la station DME (D), de l'information de synchronisation (SYD) codée sous forme d'une pluralité d'impulsions successives, dont l'espacement est spécifique ; - une étape de réception de l'information radioélectrique de synchronisation par un récepteur de type DME (DS) associé à la station MLS esclave (S), de décodage et de transmission de l'information de synchronisation (SYS) à la station MLS esclave. 1. Method for radio synchronization of at least two stations of an MLS type landing aid system, one of the stations, known as the master MLS station, providing synchronization information for the another station, called a slave MLS station, said method being characterized in that it comprises: - a step of transmitting synchronization information (S YA ) from the master MLS station (AZ) to a DME type station (D) which is associated with it; a step of radio transmission by the DME station (D) of the synchronization information (S YD ) coded in the form of a plurality of successive pulses, the spacing of which is specific; a step of reception of the radio synchronization information by a DME type receiver (D S ) associated with the slave MLS station (S), of decoding and transmission of the synchronization information (S YS ) to the station MLS slave. 2. Procédé selon la revendication 1, caractérisé par le fait que l'information de synchronisation est codée sous forme d'une suite de trois impulsions, dont les espacements sont différents des espacements des impulsions DME standard.2. Method according to claim 1, characterized in that the synchronization information is coded in the form of a series of three pulses, the spacings of which are different from the spacings of the standard DME pulses. 3. Procédé selon l'une des revendications précédentes, caractérisé par le fait que la station MLS maître est la station azimut (AZ).3. Method according to one of the preceding claims, characterized in that the master MLS station is the azimuth station (A Z ). 4. Procédé selon l'une des revendications précédentes, caractérisé par le fait qu'il comporte en outre une étape de transmission de l'état de la station MLS esclave à la station MLS maître, cette étape comportant les sous-étapes suivantes : - transmission de l'information d'état (E) de la station MLS esclave (S) au récepteur DME (DS) qui lui est associé ; - émission radioélectrique, par le récepteur DME (DS), de l'information d'état (E) codée sous forme d'une pluralité d'impulsions successives, dont l'espacement est spécifique ; - réception de l'information radioélectrique d'état (E) par la station DME (D) associée à la station MLS maître (AZ); - décodage et transmission de l'information d'état par la station DME (D) à la station MLS maître. 4. Method according to one of the preceding claims, characterized in that it further comprises a step of transmitting the state of the slave MLS station to the master MLS station, this step comprising the following substeps: - transmission of status information (E) from the slave MLS station (S) to the DME receiver (D S ) associated with it; - radio transmission, by the DME receiver (D S ), of the status information (E) coded in the form of a plurality of successive pulses, the spacing of which is specific; - reception of radio state information (E) by the DME station (D) associated with the master MLS station (A Z ); - decoding and transmission of the status information by the DME station (D) to the master MLS station. 5. Station DME (D) pour la mise en oeuvre du procédé selon l'une des revendications 1 à 3, comportant : une antenne (AD) ; un récepteur-décodeur (RX), relié à cette antenne et assurant la reconnaissance des impulsions d'interrogation DME standard ; un codeur (C) assurant la génération d'impulsions DME standard en réponse aux impulsions d'interrogation DME, et un émetteur (TX), relié à l'antenne, assurant l'émission des impulsions engendrées par le codeur ; la station DME étant caractérisée par le fait que le codeur (C) comporte en outre des moyens (CSY) de codage de l'information de synchronisation (SYA) reçue de la station MLS maître (AZ), sous forme d'une pluralité d'impulsions successives dont l'espacement est spécifique.5. DME station (D) for implementing the method according to one of claims 1 to 3, comprising: an antenna (A D ); a receiver-decoder (R X ), connected to this antenna and ensuring the recognition of standard DME interrogation pulses; an encoder (C) ensuring the generation of standard DME pulses in response to the DME interrogation pulses, and a transmitter (T X ), connected to the antenna, ensuring the emission of the pulses generated by the encoder; the DME station being characterized by the fact that the coder (C) further comprises means (C SY ) for coding the synchronization information (S YA ) received from the master MLS station (A Z ), in the form of a plurality of successive pulses whose spacing is specific. 6. Récepteur de type DME (DS) pour la mise en oeuvre du procédé selon l'une des revendications 1 à 3, caractérisé par le fait qu'il comporte : - une antenne (AS) apte à recevoir les émissions de la station DME (D) ; - un récepteur-décodeur (RXS) relié à cette antenne, assurant la reconnaissance de l'information de synchronisation codée et émise par la station DME (D) et fournissant un signal de synchronisation dit maître (SM). 6. DME type receiver (D S ) for implementing the method according to one of claims 1 to 3, characterized in that it comprises: - an antenna (A S ) capable of receiving the emissions from the DME station (D); - a receiver-decoder (R XS ) connected to this antenna, ensuring the recognition of the synchronization information coded and transmitted by the DME station (D) and providing a synchronization signal said master (S M ). 7. Récepteur selon la revendication 6, caractérisé par le fait qu'il comporte de plus : - une horloge locale (H) ; - des moyens de génération (21) d'une période de cycle MLS à partir des signaux de l'horloge locale, fournissant un signal de synchronisation dit esclave (SE), fourni à la station MLS esclave (S). 7. Receiver according to claim 6, characterized in that it further comprises: - a local clock (H); - means for generating (21) an MLS cycle period from the local clock signals, supplying a synchronization signal called slave (SE), supplied to the slave MLS station (S). 8. Récepteur selon la revendication 7, caractérisé par le fait qu'il comporte de plus des moyens d'asservissement (22-29) du signal de synchronisation esclave (SE) sur le signal de synchronisation maître (S M).8. Receiver according to claim 7, characterized in that it further comprises servo means (22-29) of the slave synchronization signal (SE) on the master synchronization signal ( S M ). 9. Récepteur selon la revendication 8, caractérisé par le fait que les moyens d'asservissement assurent la conservation de la périodicité du signal de synchronisation esclave (SE) en l'absence du signal de synchronisation maître (SM), assurant ainsi l'autonomie du récepteur.9. Receiver according to claim 8, characterized in that the servo means ensure the conservation of the periodicity of the slave synchronization signal (SE) in the absence of the master synchronization signal (S M ), thus ensuring the receiver autonomy. 10. Récepteur selon la revendication 9, caractérisé par le fait qu'il comporte des moyens (31) pour limiter dans le temps l'autonomie du récepteur à une durée prédéterminée.10. Receiver according to claim 9, characterized in that it comprises means (31) for limiting in time the autonomy of the receiver to a predetermined duration.
EP86400022A 1985-01-11 1986-01-07 Method for radioelectrically synchronizing stations of an MLS landing aid system by a DME station, and devices for carrying out such a method Withdrawn EP0191657A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8500402A FR2576111B1 (en) 1985-01-11 1985-01-11 RADIOELECTRIC SYNCHRONIZATION OF STATIONS OF AN MLS TYPE LANDING ASSISTANCE SYSTEM BY A DME STATION, AND DEVICES FOR IMPLEMENTING SUCH A METHOD
FR8500402 1985-01-11

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EP (1) EP0191657A1 (en)
JP (1) JPS61167243A (en)
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Publication number Priority date Publication date Assignee Title
JPS63238482A (en) * 1987-03-26 1988-10-04 Japan Radio Co Ltd Mls receiver

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0082770A1 (en) * 1981-12-18 1983-06-29 Thomson-Csf MLS microwave landing system with separated elevation and azimuth stations

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0082770A1 (en) * 1981-12-18 1983-06-29 Thomson-Csf MLS microwave landing system with separated elevation and azimuth stations

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CA1247217A (en) 1988-12-20
JPS61167243A (en) 1986-07-28
FR2576111A1 (en) 1986-07-18
FR2576111B1 (en) 1987-02-13

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